Dementia looks different in diabetic brain: study

CHICAGO Mon Jan 12, 2009 4:00pm EST

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CHICAGO (Reuters) - People with diabetes who develop dementia have different types of brain changes than others with dementia, a finding that could change the way drug companies think about treatments for Alzheimer's, U.S. researchers said on Monday.

"It suggests that there may be two pathways contributing to the dementia," Suzanne Craft of the Veterans Affairs Puget Sound in Washington, who worked on the study, said in a telephone interview. "These two pathways may require different forms of treatment."

Her study, reported in the Archives of Neurology, is among the first to compare different brain injuries in diabetics and others with dementia, and it found some curious differences.

Non-diabetics with dementia had an excess of sticky clumps in the brain known as beta-amyloid plaques, while diabetics, especially those who took insulin, had injuries to small blood vessels in the brain known as arterioles and more swelling in nerve tissue, Craft and colleagues found.

She said most of the people in the study had Alzheimer's disease, the most common form of dementia, and most shared similar symptoms of dementia before their deaths.

"Despite those similarities, they had very different patterns of injury to the brain," she said.

Craft and colleague Dr. Joshua Sonnen of the University of Washington, Seattle, analyzed the brains of 196 people who agreed to the autopsies after death as part of a study of dementia.

Their cases were divided into four groups: those with diabetes and dementia, those with diabetes but not dementia, those with dementia but not diabetes and those without either disease.

The team found little difference in the brain structures of 125 people without dementia, regardless of whether the person had diabetes.

But among the 71 people with dementia the researchers saw distinct differences.

Those who had dementia with no diabetes had bigger buildups of beta-amyloid, a hallmark of Alzheimer's disease. Those with diabetes had more damage to tiny blood vessels, but only those who had received treatment for diabetes, most often insulin.

Patients with dementia and untreated diabetes had beta-amyloid build-up similar to non-diabetic patients with dementia.

Craft said the study raises a lot of new questions, including what role insulin plays in the development of Alzheimer's, particularly in diabetics, who are more prone to dementia than others.

"Things get murkier before they get clearer. That is the state we are in now," she said.

She said the findings may lead to a better understanding of what causes people to develop dementia in the first place, and it might suggest ways to prevent dementia.

Alzheimer's disease is the most common form of dementia among older people. There is no cure for Alzheimer's, and current drugs merely delay symptoms.

(Editing by Maggie Fox)

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